A Porous Sulfonated 2D Zirconium Metal–Organic Framework as a Robust Platform for Proton Conduction

Abstract

By using the strategy of pre-assembly chlorosulfonation applied to a linker precursor, the first sulfonated zirconium metal-organic framework (JUK-14) with twodimensional (2D) structure, was synthesized. Single-crystal Xray diffraction reveals that the material is built of Zr 6 O 4 (OH) 4 (COO) 8 oxoclusters, doubly 4-connected by angular dicarboxylates, and stacked in layers spaced 1.5 nm apart by the presence of sulfonic groups. JUK-14 exhibits excellent hydrothermal stability, permanent porosity confirmed by gas adsorption studies, and shows high (> 10 À 4 S/cm) and low (< 10 À 8 S/cm) proton conductivity under humidified and anhydrous conditions, respectively. Post-synthesis inclusion of imidazole improves the overall conductivity increasing it to 1.7 × 10 À 3 S/cm at 60 °C and 90 % relative humidity, and by 3 orders of magnitude at 160 °C. The combination of 2D porous nature with robustness of zirconium MOFs offers new opportunities for exploration of the material towards energy and environmental applications.

Effect of Missing-Linker Defects and Ion Exchange on Stability and Proton Conduction of a Sulfonated Layered Zr-MOF

“…The electrochemical impedance spectroscopy (EIS) measurements were performed for JUK-14_MeOH and JUK-14_HCl materials at 30, 45, 60, 75, and 90% relative humidity (RH) in the temperature range of 25–60 °C (Figure a and ESI, Figures S25, S26). In order to get a complete picture of the effect of defects and the presence of the Me 2 NH 2 + ions on proton conductivity, the results obtained were also compared with the values reported earlier for the JUK-14 MOF after soaking in water, which is denoted in this work as JUK-14_H 2 O . Comparing JUK-14_MeOH and JUK-14_H 2 O , higher conductivity is observed for the methanol-soaked material (Figure c), which, like the water-soaked one, has dimethylammonium cations, but is not defective, i.e., contains more sulfonate groups, which leads to the conclusion that the poorly basic, but hydrophilic sulfonate groups may contribute to the proton conductivity by forming a more dense hydrogen bond network.…”

“…In the previous work, JUK-14 (after soaking in methanol, here denoted as JUK-14_MeOH) was presented as a material that possesses permanent porosity. 21 Here, we demonstrate an improved analysis of both the porosity and stability of this material (with a slightly modified activation procedure, see ESI), as well as the comparison with JUK-14_H 2 O and JUK-14_HCl materials.…”

Two Stable Cd-MOFs as Dual-Functional Materials with Luminescent Sensing of Antibiotics and Proton Conduction

“…It is well known that the proton conductivity of MOFs mainly depends on the concentration of proton carriers and the formation of effective proton-transport pathways. 33,81 Among them, the formation of continuous hydrogen-bonding networks is helpful to the improvement of proton conductivity. 82 A detailed structural analysis of 1 and 2, shows that although the hydrogen-bonding networks of both 1 and 2 are not continuous (Figure 1c,f), both of them show relatively high proton conductivity.…”

Remarkable proton conducting behavior driven by synergistic effects in acid–base conjugated MOFs impregnated with sulphuric acid molecules

“…[24][25][26][27] Unlike tightly packed ionic crystals, MOFs have large pore spaces to avoid ion aggregation caused by spatial congestion. [28][29][30][31][32][33][34][35][36][37][38][39][40] Unfortunately, the strategies to further reinforce the proton conductivity by enhancing charge separation are still scarce.…”